Cortical stimulation mapping for localization of visual and auditory language in pediatric epilepsy patients.

OBJECTIVE: To determine resection margins near eloquent tissue, electrical cortical stimulation (ECS) mapping is often used with visual naming tasks. In recent years, auditory naming tasks have been found to provide a more comprehensive map. Differences in modality-specific language sites have been found in adult patients, but there is a paucity of research on ECS language studies in pediatric patients. The goals of this study were to evaluate word-finding distinctions between visual and auditory modalities and identify which cortical subregions most often contain critical language function in a pediatric population. METHODS: Twenty-one pediatric patients with epilepsy or temporal lobe pathology underwent ECS mapping using visual (n = 21) and auditory (n = 14) tasks. Fisher's exact test was used to determine whether the frequency of errors in the stimulated trials was greater than the patient's baseline error rate for each tested modality and subregion. RESULTS: While the medial superior temporal gyrus was a common language site for both visual and auditory language (43.8% and 46.2% of patients, respectively), other subregions showed significant differences between modalities, and there was significant variability between patients. Visual language was more likely to be located in the anterior temporal lobe than was auditory language. The pediatric patients exhibited fewer parietal language sites and a larger range of sites overall than did adult patients in previously published studies. CONCLUSIONS: There was no single area critical for language in more than 50% of patients tested in either modality for which more than 1 patient was tested (n > 1), affirming that language function is plastic in the setting of dominant-hemisphere pathology. The high rates of language function throughout the left frontal, temporal, and anterior parietal regions with few areas of overlap between modalities suggest that ECS mapping with both visual and auditory testing is necessary to obtain a comprehensive language map prior to epileptic focus or tumor resection.

Cortical Language Areas and Plasticity in Pediatric Patients With Epilepsy: A Review.

Chronic injury to the brain from seizure activity is associated with decreased language skills in pediatric patients, as measured on neuropsychological tests for language function and academic achievement. This makes the study of language in patients with epilepsy clinically necessary. Functional magnetic resonance imaging and direct electrical cortical stimulation have been used to evaluate aspects of cortical language processing in healthy adults and in adults with epilepsy or other neurological insults. Results of these studies help to locate cortical language areas that are involved with modality-specific language processing (visual naming, auditory naming, sentence-completion, and repetition) and the neuroplasticity of language areas in the setting of neurological injury and reorganization. A better understanding of language processing contributes to a more efficient and efficacious electrical cortical stimulation mapping of language areas for patients with intractable epilepsy who are undergoing preresection evaluation. Most of the current literature on localization and reorganization of cortical language areas in the setting of epilepsy concerns the adult patient population, whereas the literature on pediatric patients is substantially lacking in comparison. This article reviews the conclusions drawn thus far from Wada, magnetoencephalography, functional magnetic resonance imaging, and electrical cortical stimulation language studies on types of language reorganization seen in pediatric patients with intractable temporal lobe epilepsy and the clinical factors associated with reorganization, and proposes future directions of research to further the academic and clinical understanding of language processing in pediatric patients.

Intraoperative ECoG During MRI-Guided Laser-Interstitial Thermal Therapy for Intractable Epilepsy.

MRI-guided laser-interstitial thermal therapy is a new modality for epilepsy surgery. In patients with intractable localization-related seizures, it has been used to ablate epileptogenic lesions with less morbidity than conventional craniotomies, and with potentially similar rates of seizure freedom. It is gaining favor in the treatment of mesial temporal sclerosis, in which the circumscribed epileptic focus is amenable to a stereotactic approach. In some centers, intraoperative electrocorticography (ECoG) is a standard procedure during tailored temporal lobectomies that include resection of mesial temporal structures. Results of intraoperative ECoG have been used to guide the extent of resection of mesial temporal structures and for prognostication. Given the limitations of burr-hole access during laser-interstitial thermal therapy, ECoG has not previously been applied. We present two case reports involving intraoperative ECoG monitoring with a depth electrode placed into the parahippocampal region, with recording before and immediately after thermal ablation of the mesial temporal region. In each case, there were decreases in the mesial temporal spike activity after laser ablation of the hippocampus. This is the first demonstration of intraoperative neurophysiologic motoring during laser-interstitial thermal therapy. The role of intraoperative ECoG for guiding the extent of ablation and determining prognosis during MRI-guided laser-interstitial thermal therapy remains to be determined.

Multimodality word-finding distinctions in cortical stimulation mapping.

BACKGROUND: Cortical stimulation mapping (CSM) commonly uses visual naming to determine resection margins in the dominant hemisphere of patients with epilepsy. Visual naming alone may not identify all language sites in resection-prone areas, prompting additional tasks for comprehensive language mapping. OBJECTIVE: To demonstrate word-finding distinctions between visual, auditory, and reading modalities during CSM and the percentage of modality-specific language sites within dominant hemisphere subregions. METHODS: Twenty-eight patients with epilepsy underwent CSM by the use of visual, auditory, and sentence-completion tasks. Hierarchical logistic regression analyzed errors to identify language sites and provide modality-specific percentages within subregions. RESULTS: The percentage of sites classified as language sites based on auditory naming was twice as high in anterior temporal regions compared with visual naming, marginally higher in posterior temporal areas, and comparable in parietal regions. Sentence completion was comparable to visual and auditory naming in parietal regions and lower in most temporal areas. Of 470 sites tested with both visual and auditory naming, 95 sites were distinctly auditory, whereas 48 sites were distinctly visual. The remaining sites overlapped. CONCLUSION: Distinct cortical areas were found for distinct input modalities, with language sites in anterior tip regions found most often by using auditory naming. The vulnerability of anterior temporal tip regions to resection in this population and distinct sites for each modality suggest that a multimodality approach may be needed to spare crucial language sites, if sparing those sites can be shown to significantly reduce the rate of postoperative language deficits without sacrificing seizure control.

Reorganization and stability for motor and language areas using cortical stimulation: case example and review of the literature.

The cerebral organization of language in epilepsy patients has been studied with invasive procedures such as Wada testing and electrical cortical stimulation mapping and more recently with noninvasive neuroimaging techniques, such as functional MRI. In the setting of a chronic seizure disorder, clinical variables have been shown to contribute to cerebral language reorganization underscoring the need for language lateralization and localization procedures. We present a 14-year-old pediatric patient with a refractory epilepsy disorder who underwent two neurosurgical resections of a left frontal epileptic focus separated by a year. He was mapped extraoperatively through a subdural grid using cortical stimulation to preserve motor and language functions. The clinical history and extensive workup prior to surgery is discussed as well as the opportunity to compare the cortical maps for language, motor, and sensory function before each resection. Reorganization in cortical tongue sensory areas was seen concomitant with a new zone of ictal and interictal activity in the previous tongue sensory area. Detailed neuropsychological data is presented before and after any surgical intervention to hypothesize about the extent of reorganization between epochs. We conclude that intrahemispheric cortical plasticity does occur following frontal lobe resective surgery in a teenager with medically refractory seizures.

Identification of distinct and overlapping cortical areas for bilingual naming and reading using cortical stimulation. Case report.

A bilingual pediatric patient who underwent tumor resection was mapped extraoperatively using cortical stimulation to preserve English and Hebrew languages. The authors mapped both languages by using 4 tasks: 1) English visual naming, 2) Hebrew visual naming, 3) read English/respond Hebrew, and 4) Hebrew reading. Essential cortical sites for primary and secondary languages were compared, photographically recorded, and plotted onto a schematic brain of the patient. Three types of sites were found in this patient: 1) multiuse sites (multiple tasks, both languages) in frontal, temporal, and parietal areas; 2) single-task sites (1 task, both languages) in postcentral and parietal areas; and 3) single-use sites (1 task, 1 language) in frontal, temporal, and parietal areas. These results lend support to the concept that bilingual patients can have distinct cortical representations of each language and of different language tasks, in addition to overlapping or shared sites that support both languages and multiple tasks.